The printing industry and, in particular, the graphic arts industry requires the transfer of photographs in the form of transparencies from the actual transparency to a print medium such as paper. Typically, the publication of a typical weekly magazine requires hundreds of such transfers. In accomplishing the transfers, and, in particular, with respect to the covers of such magazines, great care must be taken to be assured that the transfer of the colors from the transparencies are accurate with respect to printed picture. This is required in that ideally, the color art work or packaging should be aesthetically pleasing to the eye and accurate with respect to the original transparency.
Optical scanning methods and apparatus have been developed which electronically read the transparency and transfer the data to a four color photosensitive material. Examples of these scanning methods can be found in U.S. Pat. Nos. 4,613,896; 4,189,741; 4,684,979; 4,899,214; 4,473,848; and 2,548,783. The aforementioned patents illustrate the variety of methods in which the optical scanner transfers the images and colors read from the transparency to the photosensitive material, referred to in the industry as a proof. Typically, the transparency in a size from 35 mm up to 11.times.14 inches is positioned on a rotating drum. The scanner drum itself is a transparent hollow plastic cylinder approximately 30 inches in length and approximately 8 inches in diameter with the clear plastic cylinder itself being approximately 3/8 inch in thickness. At each end of the cylinder there are circular mounting plates approximately 1/2 inch in thickness with an approximately 31/2 inch bore in each plate for the accurate centering and positioning of the drum on the scanner itself. The transparency is then mounted on the outer surface of the scanner drum and the drum is placed in the scanner in a horizontal position and is then spun at a high speed as a laser passes over the transparency image reading the image through fiber optics, breaking the image down into four separate colors, yellow, magenta, cyan and black. That information is then transferred to a receiving drum on which negative film is mounted, thus giving the physical four-color film that is necessary for the printing process. Once the initial transfer is made, color adjustments are usually required. The first transfer, representing a four-color proof, is compared with the original transparency. The operator, in accomplishing this comparison, must remove the transparency from the scanner drum and view the transparency on a light box or proof light illuminator.
The standard light source used in the graphic arts industry for the comparison of the transparency and the negative is what is commonly referred to as 5000 Kelvin lighting or 5000 K. This illumination standard is used in that it is a true "white" light that contains all colors of the spectrum in approximately equal amounts. Therefore, it illuminates all color with equal effectiveness and without distortion. Most commercial light sources, such as incandescent or cool-white fluorescent lighting, emphasize some spectrum colors and deemphasize others making them unsuitable for critical appraisal of colors. In making the comparison, the operator would therefore place the transparency on a 5000 K proof-light illuminator and subject the four-color proof to an overhead 5000 K light source. If the proof does not match the transparency under these conditions, the entire procedure of scanning the transparency would then have to be repeated with appropriate color adjustments. This would require resetting the coordinates for the transparency on the scanner drum and reading the transparency again by laser thereby developing a second proof.
As a standard practice, some operators rather than removing the transparency, place the entire scanning drum in front of a 5000 K proof-light illuminator and attempt to interpret the color of the transparency as compared to the four-color proof. Unfortunately, the distance of the transparency mounted on the drum to the surface of the 5000 K light source makes this type of comparison inaccurate and undesirable.
The present invention directs itself to a structure and process whereby the transparency can be viewed while still secured to the standard scanner drum by means of positioning the 5000 K light source within the drum. By means of this apparatus and process described hereafter, the operator can determine the color comparison between the transparency and the proof, and if unsuitable or color adjustments are required, the transparency can then be scanned a second time without the need for the resetting of the coordinates with the optical scanner, thus saving substantial time yet ensuring a critical comparison under the light source conditions which are the standard in the industry.